The proposed work is aimed at a complex analysis of the enzymologyof DNA replication in herpes simplex virus infected cells. Several enzymes have been purified (DNA polymerase, DNase, deoxypyrimidine kinase), a new one has been identified (deoxypyrimidine triphosphatase), while others so far are known only as genetic loci (ts B, ts J, ts L, ts S, ts U, etc.). Our combined genetic-biochemical approach utilizes viral temperature-sensitive mutants and cell-free DNA synthesis systems. The goal of this work is to analyze the multienzyme complex responsible for viral DNA replication as a basis for the understanding of herpes simplex virus multiplication during lytic infection, latency and malignant transformation.